Cutaneous T-cell Lymphoma (CTCL) is a clonally derived skin invasive malignancy of CD4+ T-cells. Patients with advanced forms of CTCL characterized by multiple tumors or peripheral blood involvement typically have a poor prognosis, yet often are quite responsive to manipulation of host anti-tumor immunity, such as with interleukin-12 (IL-12) administration. Our previous work has demonstrated that advanced CTCL is characterized by prominent immunologic defects including depressed cell-mediated immunity. A marked defect in IL-12 production in CTCL has also been noted, which may play a role in depressed cell-mediated immunity. Because antigen presenting cells, particularly dendritic cells (DCs), are the most potent source of IL-12, we will examine DCs from the blood and skin of CTCL patients in an effort to define the possible relationship between impaired cell-mediated immunity and abnormalities in DC populations. Our preliminary data indicate 1) a stage related decrease in both CD11c+ and CD123+ circulating DCs; 2) a marked depression in IL-12 and IFN-( production by patient DCs; 3) a marked abnormality of the CD40-CD40 ligand system; 4) correction of the defect in IL-12 production when patient cells are cultured with a novel recombinant mega CD40 ligand; 5) the possible decreased expression of certain toll like receptors on CTCL patient DCs correlating with decreased cytokine production in response to microbial DNA. We propose to more fully characterize these defects and relate the causally to production of soluble factors released by malignant T-cells. We will also test in vitro CD40 ligand and repeat CpG oligonucleotides, known to activate normal DCs, for their ability to induce activation, growth, cytokine production and enhance NK activity in preparation for clinical trials. As part of another proposal, CTCL patients will enroll in phase II trials administering either recombinant IL-12 or CpGs. DC numbers and function will be assessed prior to, during and after treatment with these agents. Global gene expression profiles before manipulation and after treatment of DCs with CD40L, CpGs and IL-12 will be performed using cDNA microarrays. Studies which enhance our understanding of the immunologic defects that occur and the mechanisms of action of biological agents should ultimately permit the development of strategies for the optimal enhancement of anti-tumor immunity with combinations of immune augmenting therapeutics.